Microdialysis measurements of equine lamellar perfusion and energy metabolism in response to physical and pharmacological manipulations of blood flow.
Authors: Medina-Torres C E, Underwood C, Pollitt C C, Castro-Olivera E M, Hodson M P, Richardson D W, van Eps A W
Journal: Equine veterinary journal
Summary
# Editorial Summary Evaluating lamellar blood flow and metabolic function in horses has proven technically challenging, yet understanding perfusion changes is critical for managing and preventing laminitis. Researchers implanted microdialysis probes into the lamellar tissue and skin of nine Standardbred horses to measure urea clearance (as a perfusion marker) alongside energy metabolites—glucose, lactate and pyruvate—under various conditions including tourniquet application, norepinephrine and potassium chloride infusions, and systemic acetylpromazine administration. Severe ischaemia from tourniquet application produced the most dramatic metabolic shifts: lamellar glucose fell significantly whilst lactate, urea and lactate:glucose ratios all increased markedly, whereas skin dialysate remained largely unchanged. More subtle perfusion changes—induced by norepinephrine or acetylpromazine—were detectable through alterations in glucose and lactate metabolism even when urea clearance showed minimal change, suggesting that metabolite ratios are more sensitive indicators of borderline perfusion compromise than urea clearance alone. This microdialysis approach offers practitioners and researchers a quantifiable method for tracking lamellar metabolic dysfunction during laminitis progression and for assessing the efficacy of vasoactive drugs, potentially enabling earlier intervention before irreversible tissue damage occurs.
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Practical Takeaways
- •Microdialysis metabolite measurements are more sensitive than urea clearance for detecting subtle lamellar perfusion changes and may help evaluate vasoactive therapies in laminitis management
- •Severe tourniquet-induced ischaemia causes distinctive metabolic shifts (lactate accumulation, glucose depletion) that mirror early laminitis pathophysiology
- •This technique offers a non-invasive method to monitor lamellar metabolic status and assess effectiveness of perfusion-enhancing treatments during laminitis development
Key Findings
- •Tourniquet application caused severe lamellar hypoperfusion with decreased glucose and increased lactate, urea, and lactate:glucose ratio
- •Norepinephrine infusion decreased glucose and increased lactate:glucose ratio at both lamellar and skin sites without significant urea clearance changes
- •KCl caused decreased lactate:glucose ratios in lamellar and skin tissue without affecting urea clearance
- •Acetylpromazine produced profound lamellar metabolic changes (decreased glucose and lactate:pyruvate, increased lactate:glucose) without detectable perfusion changes by urea clearance